St. Athanasius (c. 296–373 AD) is a prominent Church Father and Doctor of the Church, renowned for his staunch defense of Trinitarian doctrine against Arianism. Born in Alexandria, Egypt, he became a deacon under St. Alexander of Alexandria and succeeded him as bishop in 328 AD. Athanasius is best known for his role in the First Council of Nicaea in 325 AD, where he championed the Nicene Creed, affirming the divinity of Christ.

Throughout his life, St. Athanasius faced numerous challenges, including multiple exiles due to his opposition to Arianism and his commitment to orthodox Christianity. His writings, particularly "On the Incarnation," are influential in Christology and have shaped Christian theology. Revered as a saint in both the Catholic and Eastern Orthodox Churches, his feast day is celebrated on May 2. Athanasius is often called the "Father of Orthodoxy" for his unwavering dedication to the faith and his significant contributions to the development of Christian doctrine.